Triode electron gun with positive grid and modular cathode

ABSTRACT

Triode electron gun with positive control grid, with emitting cathode, and with acceleration anode, providing a concentration and emission of electrons directed along straight and parallel paths. Thus gun includes several elementary guns distributed around a single axis, the axes of the guns converging toward one and the same point on the axis situated at the entrance to an axial conical conduit drilled in the anode. The electrons produced in each elementary gun by an emitting pellet go through a concentrator and then through a conduit in alignment with the axis of each gun and perforated in a single thick grid. The invention can be applied in metallurgy for melting and heating.

United States Patent Sommeria [4 1 May 16, 1972 s41 TRIODE ELECTRON GUN WITH 3,107,313 10/1963 Hechtel ..313/299 x TI E R AND MODULAR 3,497,743 2/1970 Wal ch et aI. CATHODE 3,558,967 1/ 1971 M1r1am ..3 l5/3.5

inventor: Jean Sommeria, Annecy, France Societe Alsacienne De Constructions Atomiques De Telecommunications Et DElectronique Alcatel,", Paris, France Filed: July 29, 1970 Appl. No.: 59,224

Assignee:

Int. Cl ..l'l0lj 29/04, HOlj 29/48, HOlj 29/56, Field of Search ..313/82 R, 70 R, 69 R References Cited UNITED STATES PATENTS 8/1957 Diemer ..3l3/70 X Primary Examiner-Robert Segal Att0rr1eySughrue, Rothwell, Mion, Zinn & Macpeak 57] ABSTRACT Triode electron gun with positive control grid, with emitting cathode, and with acceleration anode, providing a concentration and emission of electrons directed along straight and parallel paths. Thus gun includes several elementary guns distributed around a single axis, the axes of the guns converging toward one and the same point on the axis situated at the entrance to an axial conical conduit drilled in the anode. The electrons produced in each elementary gun by an emitting pellet go through a concentrator and then through a conduit in alignment with the axis of each gun and perforated in a single thick grid. The invention can be applied in metallurgy for melting and heating.

5 5 Claims, 1 Drawing Figure Patented May 16, 1972 3,663,853

TRIODE ELECTRON GUN WITH POSITIVE GRID AND MODULAR CATHODE BACKOROUN D OF THE INVENTION This invention concerns improvements in the triode electron gun described in the U.S. Pat. application No. 818,735, filed on Apr. 23, 1969, involving a heat-emitting cathode, a control grid, and a polarized acceleration anode.

In this type of electric gun, an attempt has been made to create the conditions which will make it possible to generate electron flows that will be as parallel as possible while using relatively low-intensity electrical fields. We know that, in order to obtain such parallel electron flows, we generally subject the emitting cathodes to electrical fields with intensive acceleration. Now, the utilization of such electrical fields entails potential differences between the anode and the cathode, whose value rapidly becomes prohibitive.

SUMMARY OF THE INVENTION In this invention, the method involved consists in clearly separating the space for the extraction of the electrons from the acceleration space. We thus get a straight electron flow in an extraction space by creating a large electrical field between the cathode and a control acceleration grid but the voltage difference between the anode and this control acceleration grid remains within the usual limits.

Internal arrangements make it possible to obtain a parallel flow in the extraction space so that the trajectories of the electrons of the elementary bundles of electrons, which pass through the mesh of the screen-grid and the mesh of the polarized grid, are parallel.

The invention is intended to improve this process by making the emission zones on the emitting cathode even more homogeneous and absolutely straight and the trajectories of the electrons in the extraction zone more parallel to each other.

To make the emitting surface more homogeneous, the improvement is based on the following considerations. We know that the distribution of the heat produced by a heating means on an emission surface is not homogeneous and we can obtain a more homogeneous emission by dividing the emission surfaceinto identical surface elements and by heating all of these surface elements in the same manner. For this purpose we use, for each of these elements, a separate heating unit and we arrange these heating units in the same manner with respect to the surface elements. Finally, we replace the modular electronic gun with elementary guns identical to each other.

Furthermore, to make the path of the electrons parallel, the improvement involves making these electrons pass into cylindrical conduits whose cross-section is small and whose length is rather great. In the electron gun which we want to improve, the mesh of the screen-grid and the mesh of the polarized grid have identical forms and are placed one above the other so as to make up cylindrical studs. But, to obtain a large electrical field without using very great potential differences, we must move the grids closer together which damages the parallel arrangement of the trajectories of the electrons.

An attempt was therefore made to find a solution making it possible to constitute for the passage of the electrons into the grids cylindrical studs having a relatively small crosssection and a relatively great length.

Finally, we used a very thick grid that was polarized with respect to the emitting cathodes and we drilled small-section cylindrical studs into this grid, opposite each one of the elementary emitting cathodes.

In this way, an electron gun thus improved involving an emitting cathode, a control grid, an acceleration anode, and in which the place where the physical phenomenon of the extraction of the electrons occurs is separated from the place where the physical phenomenon of the acceleration of these electrons occurs by placing each of these phenomena in an electrically defined space, the spaces being contiguous and their separation being perfectly defined is characterized by the fact that the extraction place is constituted by the assembly of several identical emitting cathodes, each having its own heating unit and the place of acceleration is constituted by a grid that is polarized with respect to the emitting cathodes, said grid being very thick and, in front of each of the emitting cathodes, representing a cylindrical conduit with a relatively narrow cross-section, the direction of said conduits being that of the axes of emission of the cathodes and the axes of emission of the cathodes and of the cylindrical conduits converging at a point situated on the axis of the acceleration anodes.

The advantage offered by the electron gun, thus improved, is that the speeds of emission of the electrons in the elementary guns are made more uniform than in the modular single gun described in U.S. Pat. application No. 818,735. In the improved gun it is therefore easier to concentrate the electrons on the entrances of the conduits hollowed out in the control grid.

Another advantage of the improved electron guns is to constitute rather very narrow and relatively long conduits which force the path of the electrons to be parallel and to constitute very essentially monokinetic electron flows.

Another advantage is the ability to concentrate on the level of the acceleration anode and on the axis of this anode all of the electron beams coming from elementary guns and the ability to obtain great electrical power in the overall beam of the modular gun.

BRIEF DESCRIPTION OF THE DRAWINGS The improvement will be better understood in the course of the following description of one version of the electron gun, given here by way of non-restrictive example, referring to the attached drawing on which the single FIGURE is an elevational view in cross-section of the modular gun.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gun of the present invention involves a tight cylindrical metallic gear-case l in which it is possible to create a vacuum and whose axis is that of the modular gun. A crown 2, attached to the wall of gear-case 1, serves as support for a circular support 3, made of insulating material, which carries a metallic socket 4 involving wide openings allowing passage to the electrical conductors to which voltage is applied.

A case 5, in a tronconic form, is attached to socket 4; the axis of this case is that of the gun and it supports the elementary electron guns 6 which serve for the emission of the electrons. In the example cited, the gun has six elementary guns 6, only two of which are visible in the figure and which are arranged around the axis of the gear-case in such a fashion that their axes are in planes passing through said axis and constituting angles of 60 among themselves, the axes of the elementary guns forming an angle of 20 with the axis of the gear-case.

To case 5 is connected an electrical conductor 7 which enters the gun parallel to the axis of the gun. Elementary guns 6 are attached to case 5 by means of washers 8.

The refractory blocks 9 carry the heating units made up, in the example considered, of the heating windings or filaments 11 of the elementary guns which are connected in parallel to conductors 12 and 13. Metal tubes 14, which have the same axis as the corresponding elementary gun, are attached to in sulating sleeves 10.

These tubes are connected electrically in parallel to a central conductor 15. Each of the tubes 14 is closed off by a pellet 16 made up of a material for emitting hot electrons. The interior of each pellet 16 has the shape of a spherical segment. Concentrators 17, attached to tubes 10, surround the emitting pellets 16.

A thick and circular grid 18 is attached to the side of case 5 so that the axis of this grid may be situated in the proximity of the cathodes of guns 6. Cylindrical conduits 19, with a small cross-section, are formed in the grid 18 so that the axis of each one of them coincides with the axis of the adjacent elementary gun 6.

A circular anode 20 is attached to gear-case l. A conical conduit 21 is perforated in the anode 20 so that its axis coincides with that of gear-case l and so that the axes of the elementary guns 6 pass through a common point on the axis of the gear-case situated at the entrance to conduit 21.

In the gun shown in the drawing, anode 20 is grounded. Grid 18 is brought by conductor 7 and case to a potential of 40,000 V with respect to the ground, and cathodes 16 are brought, by conductor 15, to a potential of 5,000 V with respect to grid 18. Filaments ll are brought to a potential of 3,000 V with respect to the cathode by conductors l2 and 13.

The electrons come out of cathodes 16 and are forced back toward the axis of these cathodes by concentrators 17. The electrical field between cathodes 16 and grid 18 is large and the electrons take on a relatively great speed and penetrate into conduits 19. The electrons, whose trajectories are not parallel to the axis of passages 19, are captured by grid 18 which can be cooled by the circulation of a fluid (not shown). Finally, essentially monokinetic parallel electron flows emerge from this grid.

If there were no voltage difference between grid 18 and anode 20, the electrons would converge on the axis of gearcase 1 toward the point of convergence of the axes of the elementary guns. No existance of a voltage difference between anode 20 and grid 18 turns the point of convergence of electron flows, coming from the elementary guns, into a point on the axis of the modular gun situated on the output of conduit 21. Beyond this conduit, the beam of electrons is picked up by a well-known magnetic optical arrangement (not shown) which makes it possible to regulate its focalization according to the intended use.

This improved electron gun can have many applications in metallurgy for melting or heating operations requiring very great power as well as for all other operations requiring a very strong energy density concentrated in the form of a narrow and orientable beam.

I claim:

1. An electron triode gun comprising an emitting cathode formed of several annularly spaced, identical tubular modules, each provided with a heating means and an emitting surface, a single very thick control grid disposed adjacent to said modules and having converging openings of small cross section therethrough in alignment with said emitting surfaces to receive electrons therefrom, and an acceleration anode disposed adjacentto said control grid and positioned on the side thereof opposite to said modules, said anode having an opening therethrough positioned to receive the electrons passing through said converging gn'd openings, the axes of said grid openings converging at a point situated on the axis of said anode opening, and each of said modules being disposed at an angle to the axis of said anode opening so that the electrons from said emitting surfaces are directed in a converging manner through said grid openings to a point situated on the axis of said anode opening, the extraction of the electrons being effected in the space between the cathode and the control grid, and the acceleration of the electrons being effected in the space between the control grid and the anode.

2. The electron triode gun according to claim 1 wherein the openings through the grid are cylindrical conduits.

3. The electron triode gun according to claim 1 wherein said cathode modules are disposed in an annular arrangement in substantially equally spaced relation.

4. The electron triode gun according to claim 3 wherein said anode opening is disposed substantially in the center of said anode.

5. The electron triode gun according to claim 1, wherein each of said modules comprises an emissive pellet surrounded by a concentrator.

i III I k i 

1. An electron triode gun comprising an emitting cathode formed of several annularly spaced, identical tubular modules, each provided with a heating means and an emitting surface, a single very thick control grid disposed adjacent to said modules and having converging openings of small cross section therethrough in alignment with said emitting surfaces to receive electrons therefrom, and an acceleration anode disposed adjacentto said control grid and positioned on the side thereof opposite to said modules, said anode having an Opening therethrough positioned to receive the electrons passing through said converging grid openings, the axes of said grid openings converging at a point situated on the axis of said anode opening, and each of said modules being disposed at an angle to the axis of said anode opening so that the electrons from said emitting surfaces are directed in a converging manner through said grid openings to a point situated on the axis of said anode opening, the extraction of the electrons being effected in the space between the cathode and the control grid, and the acceleration of the electrons being effected in the space between the control grid and the anode.
 2. The electron triode gun according to claim 1 wherein the openings through the grid are cylindrical conduits.
 3. The electron triode gun according to claim 1 wherein said cathode modules are disposed in an annular arrangement in substantially equally spaced relation.
 4. The electron triode gun according to claim 3 wherein said anode opening is disposed substantially in the center of said anode.
 5. The electron triode gun according to claim 1, wherein each of said modules comprises an emissive pellet surrounded by a concentrator. 